New Axially Chiral Sulfur Compounds: Synthesis and Conformational Stability of Enantiopure 4,4'-Biphenanthrene-3,3'-dithiol and Related Atropisomeric Derivatives

Article abstract of DOI:10.1016/0957-4166(95)00074-Y

Enantiopure (R)- and (S)-4,4'-biphenanthrene-3,3'-dithiol 1a has been prepared for the first time through a synthetic procedure involving in the key stop a stereoconservative Newman-Kwart thermorearrangement of the bis-N,N-dimethylthiocarbamoyl ester of (R)- and (S)-biphenanthrol 2b, respectively.The atropisomeric conformations of 1a are not, interconverted even at temperatures as high as 285 deg C, whereas the related biphenanthrothiophene 3 is completely racemized in a few minutes at 250 deg C.The axially chiral backbone of 1a has been incorporated in a set of novel C₂ symmetry sulfur reagents suitable for a variety of stereoselective reactions.